Identification of PWR Stainless Steel Piping Safety Significant Locations Susceptible to Stress Corrosion Cracking

摘要

Stress corrosion cracking (SCC) of stainless steel was originally considered only an issue with boiling water reactors (BWRs), but operating experience has shown that this phenomenon also occurs in pressurized water reactors (PWRs), such as in off-chemistry locations of stagnant branch connection piping. In this paper, the safety significant stainless steel piping locations susceptible to SCC are identified for three representative PWR plants (Plant A [Babcock and Wilcox-designed], Plant B [Westinghouse-designed], and Plant C [Combustion Engineering-designed]). For the purpose of this paper, "safety significant" is defined as having a high consequence of failure as determined by the plant's risk-informed in-service inspection (RI-ISI) program. Weld locations are considered susceptible to SCC when the water is stagnant and ≥200 °F during steady-state reactor operation. The results of this work will be used to develop guidance for selection of welds to inspect when addressing currently existing inspection requirements.